Balancing Coils for 10 MHz Susceptibility Signals
The de Haas-van Alphen (dHvA) effect is the low temperature oscillatory magnetization of a metal in a high magnetic field. Analysis of the oscillations yields such information as the cross sectional area of the Fermi surface extrema, the effective electron masses for extremal areas, and the electron scattering rates (or mean free paths) for the electron orbits of these areas. In the early fifties, Shoenberg1 pioneered the use of a pair of balanced pick-up coils, with a sample in one coil, in pulsed magnetic fields to measure the dHvA effect in the highest possible magnetic fields. The oscillations in these approximately 10 Tesla (T) fields were detected at a frequency of order 105 Hz. Recent work2 to measure the Fermi surface parameters of YBa2Cu3O6.97, a high temperature superconductor in fields to about 100 T produced oscillations of order 107 Hz. At these frequencies, we found that new ways had to be developed to balance coils because the capacitive reactance dominates. In this paper we describe the problems, our solutions, and the experimental results from our coils designed to operate at these higher frequencies in a system where it must work the first time.
KeywordsHigh Magnetic Field Pulse Magnetic Field Pure Epoxy Modulation Coil Early Fifty
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